TAMPA ó The plane was rising high above Ft. Lauderdale on its way to Dallas when Colby Isaac Hilleary began to panic. He left his seat, complained to a flight attendant that the plane was heading the wrong way, and knocked on the cockpit door.

"The plane is hijacked and there are no pilots," he proclaimed. As the American Airlines flight crew tried to calm him, he threw punches. Two passengers helped restrain him as the plane made an emergency landing in Tampa.

In a federal courtroom Monday morning, a psychologist told a judge that the March 2 incident was a manifestation of mental illness, and that Hilleary had no rational understanding of what he was doing.

Hilleary, 24, who has since received treatment, apologized before a judge sentenced him to five years probation.

Hilleary pleaded guilty in June to a charge of interference with a flight crew.

"Iím very embarrassed," he said Monday.

Don McMurray, the forensic psychologist who examined the defendant, testified that he had exhibited some signs of mental illness in the months before the incident.

Hilleary had come to Ft. Lauderdale from Texas to work with a crew that did construction and maintenance on yachts. During the job, he became suspicious of his co-workers, accusing them of stealing his work shifts.

The doctor related another incident in which Hilleary, at home in Texas, became paranoid and hallucinated a vision of people standing in his driveway.

The doctor did not mention a specific diagnosis, but said he had ruled out schizophrenia and physiological causes.

U.S. District Judge Steven Merryday could have given Hilleary jail time, but a prosecutor did not seek such a sentence. The judge ordered Hilleary to continue mental health treatment but also offered words of warning.

"I donít want you to walk away from here thinking that anybody is stupid," Merryday said.

"You canít afford any more foolishness. You need to grow up and conduct yourself in a manner befitting an adult."